This invention relates to communication cross-talk in detonator systems and particularly in large detonator systems.
Many electronic detonator systems use voltage modulation techniques on signals which are transmitted from a control device to an electronic detonator, and current modulation techniques on signals which are transmitted from a detonator to the control device. A large detonator system can include hundreds, if not thousands, of detonators and electrical constraints usually require that the detonators are split into segments which are electrically isolated from each other. A separate control device is used to control each segment. Each control device is connected to a master blast controller which is used to initiate the blast.
Typically the level of voltage modulation is of the order of several volts while the level of current modulation is of the order of a few milliamperes. Thus if voltage modulated signals are transmitted in one segment and current modulated signals are transmitted in an adjacent segment the level of electronic interference in the current modulated segment may be sufficiently high to disrupt communications.
In one approach which is adopted to address this problem communication is allowed in only one segment at a time in order to eliminate cross-talk between segments. In another approach communication between the controller and the detonators is repeated to ensure that the communication is successful. Each technique increases the time required for successful communication.
The invention is concerned with an alternative approach to reducing detonator cross-talk of the aforementioned kind.